Artificial Synaptic Emulators Based on MoS₂ Flash Memory Devices with Double Floating Gates

We fabricated MoS₂-based flash memory devices by stacking MoS₂ and hexagonal boron nitride (hBN) layers on an hBN/Au substrate and demonstrated that these devices can emulate various biological synaptic functions, including potentiation and depression processes, spike-rate-dependent plasticity, and spike-timing dependent plasticity. In particular, compared to a flash memory device prepared on an hBN substrate, the device fabricated on the hBN/Au exhibited considerably more symmetric and linear bidirectional gradual conductance change curves, which may be attributed to the device structure incorporating double floating gate. For the device on the hBN/Au, electron transfers may occur between the floating gate MoS₂ and Au, as well as between the floating gate MoS₂ and the channel MoS₂, allowing for more control over electron tunneling and injection. To test our hypothesis, we also fabricated a MoS₂-based flash memory device on an hBN/Pd substrate and found behavior similar to the device fabricated on hBN/Au. Our results demonstrate that flexible synaptic electronics may be implemented using MoS₂-based flash memory devices with double floating gates.